<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        div {
            margin: 3.2em;
            width: 12em;

            position: relative;
            background: #58a;
            background: linear-gradient(-150deg, transparent 1.414em, #58a 0);
            border-radius: .5em;

            padding: 2em;
            color: white;
            font: 100%/1.6 Baskerville, Palatino, serif;
        }

        div::before {
            content: '';
            position: absolute;
            top: 0;right: 0;
            background: linear-gradient(to left bottom, 
                transparent 50%, rgba(0, 0, 0, .2) 0, rgba(0, 0, 0, .4)) no-repeat 100% 0;
            width: 1.73em;
            height: 3em;
            transform:  translateY(-1.3em) rotate(-30deg);
            transform-origin: bottom right;
            border-bottom-left-radius: inherit;
            box-shadow: -.2em .2em .3em -.1em rgba(0, 0, 0, .15);
        }


    </style>
</head>
<body>
    <div>“The only way to get rid of a temptation is to yield to it.”
— Oscar Wilde, The Picture of Dorian Gray</div>
</body>
</html>